Change Range Selection With A Variable

How do I change the selection of a range with a variable, and not a hardcoded number in XL2003? I have to update a set of spreadsheets every month, and it's a hassle to have to constantly open my pivot table worksheet, copy, open the summary worksheet, paste ... etc. etc. etc. The code below is my attempt at creating a ComboBox with "January, February, March, etc." and every time I select a particular month it will automatically copy data from my pivot table worksheet into my new summary worksheet in the correct column. The range of data from my pivot table worksheet will never change, so I have no problem hardcoding that in, but based on which month is selected will alter which column the data goes in in the new worksheet.

I want to be able to write code for one month (say January) and then when I want to use a different month (say February) I can just change the column number and call up the originial January code.

Private Sub ComboBox1_Change()
Dim ColNum ' This is the variable I want to change based on which month is called
If ComboBox1.Value = "January" Then
ColNum = 1 ' Column number for Column A- Where my January column is
Elseif ComboBox1.Value = "February" Then
ColNum = 2 ' Column number for Column B- Where my February column is
' etc. etc. for each month
End If
Call January
End Sub

Private Sub January()
' Just a quick msgbox to make sure the previous macro is calling this one
MsgBox "Is this macro running?", vbQuestion + vbYesNo, "Check"...........................